1. Field of the Invention
This invention relates to a device for receiving on the ground microwaves from communication satellites, broadcasting satellites.
2. Related Background Art
Accompanying the recent rapid development of information network systems, the demand for satellite communication and broadcasting systems has rapidly increased, and frequency bands are becoming higher. In order to break through the limitation of the characteristics in Si bipolar transistor, a compound semiconductors, especially Schottky barrier field effect transistor consisting of GaAs (MESFET) has been practically used as a field effect transistor. In addition, to smaller-size the systems, reduce their prices and improve their performance, recently the integration (MMIC: Microwave Monolithic Integrated Circuit) of downconverter for converting higher frequencies to lower frequencies is being advanced.
As the antenna for directly receiving microwave signals from communication satellites and broadcasting satellites, the so-called parabolic antenna which collects electromagnetic waves by a parabolic reflecting mirror is the best in terms of efficiency and is presently most popular. On the other hand, an antenna comprising a plurality of antenna elements arranged in plane, and signal powers received by the respective elements are collected by a transmission line is called planar antenna. Owing to the improvement of the printing technique, planar antennas which are applicable to the microwave band have been available. Initially the planar antenna was far behind the parabolic antenna in terms of performance and costs. But the planar antenna has been increasing more studied since the latter half of 1970's, and the performance of the print board for microwaves has been improved. Presently the planar antenna has reached practical level.
As described above, there is possibility that the planar antenna, owing its plane structure, is able to be integrated monolithically on one and the same compound semiconductor substrate with a receiving unit to be connected to the planar antenna, i.e., a low noise amplifying circuit for amplifying a microwave signal received by the planar antenna, a frequency converting circuit for downconverting a frequency of the microwave signal amplified by the low noise amplifying circuit, a circuit for amplifying a downconverted middle-frequency signal, etc. If this integration is realized, it will be possible to reduce the size of the antenna system and simplify the connection of the antenna with the receiving unit. In addition, if the antenna can be integrated by a conventional manufacturing process for integration circuit, it will be advantageous in terms of the fabrication cost.